Sensory Systems

Question 1

How are sensory stimuli received and processed by the body?

Answer 1

1. sensory organs detect a physical or chemical stimulus in the environment
2. specialized sensory cells detect these signals and code them as information to transmit and process thru the nervous system

Question 2

What is sensory transduction?

Answer 2

the conversion of physical or chemical stimuli into nerve impulses

Question 3

What are mechanoreceptors?

Answer 3

sensory receptors that respond to physical deformations of their membrane

touch, stretch, pressure, motion, sound

Question 4

What are hair cells?

Answer 4

specialized mechanoreceptor that senses movement and mechanical vibrations

Question 4

How do hair cells work?

Answer 4

1. hair cells sense vibrations
2. vibrations move stereocilia
3. motion of stereocilia causes depolarization of the cell
4. neurotransmitters are released

Question 5

How do sound waves travel through the ear?

Answer 5

1. sound waves travel into the outer ear
2. travels thru ear canal and hits the eardrum, causing it to vibrate
3. the vibration moves the ossicles, which transmit vibration to the oval window in the cochlea

Question 6

What occurs in the basal membrane after the oval window is depressed by the ossicles?

Answer 6

1. oval window creates waves that travel thru the cochlear fluid
2. waves cause the basilar membrane to move
3. movement of basilar membrane is transmitted into electrical impulses within the Organ of Corti

Question 7

What happens to the hair cells when the basilar membrane moves?

Answer 7

1. stereocilia on top of hair cells move against the tectorial membrane
2. stereocilia bent toward the kinocilium stimulates the opening of K+ channels at the hair cell terminal, leading to depolarization

Question 8

When the stereocilia are ____, the hair cell is at rest.

Answer 8

straight

Question 9

When the stereocilia are bent ____ the kinocilium, the hair cell depolarizes, causing ____.

Answer 9

toward the kinocilium; stimulation

Question 10

When the stereocilia are bent ____ the kinocilium, the hair cell hyperpolarizes, causing ____.

Answer 10

away from; inhibition

Question 11

Hair cells at the base of the cochlea transmit ____ frequencies.

Answer 11

high

Question 12

Hair cells at the apex of the cochlea transmit ____ frequencies.

Answer 12

low

Question 13

What is the process of auditory transduction at the synapse of the hair cell and auditory nerve?

Answer 13

1. K+ ions flow out of stereocilia and into hair cell, causing depolarization
2. Depolarization stimulates the opening of Ca+ channels at the terminal
3. Excitatory neurotransmitters are released into the synaptic cleft
4. Neurotransmitters bind to ligand-gated ion channels of the afferent auditory nerve
5. EPSPs are received by the afferent auditory nerve as graded potentials, which fire as action potentials to the brain when threshold is reached
6. Signal is received by the brain and processed as sound

Question 14

What are electromagnetic receptors?

Answer 14

Sensory cells that respond to electrical, magnetic, and light stimuli

Question 15

What are photoreceptors?

Answer 15

light detecting electromagnetic receptors found in the eye

Question 16

What protein converts light energy into electrical signals?

Answer 16

opsin

Question 17

What light-absorbing pigment molecule is found in opsin?

Answer 17

retinal

Question 18

What is the resting membrane potential of photoreceptor cells?

Answer 18

-35 mV

Question 19

Why do photoreceptor cells have a more positive resting membrane potential than neurons?

Answer 19

leaky Na+ channels within the photoreceptor cells let in more Na+ ions at rest

Question 20

What are cones?

Answer 20

photoreceptor cells in the retina responsible for color vision and greater spatial acuity

Question 21

What are rods?

Answer 21

photoreceptor cells in the retina responsible for shades of grey and low light

Question 22

What is glutamate?

Answer 22

an excitatory neurotransmitter that sends signals to the brain for visual processing

Question 23

In the dark/light, photoreceptors release glutamate.

Answer 23

dark

Question 24

In the **dark/light**, photoreceptors stop releasing glutamate.

Answer 24

light

Question 25

**Cis/trans** retinal is bound to opsin in the dark.

Answer 25

cis

Question 26

**Cis/trans** retinal is bound to opsin in the light.

Answer 26

trans

Question 27

What happens in the photoreceptor cell in the dark?

Answer 27

1. cis retinal is bound to opsin 2. cGMP activates the opening of Na+ channels 3. Na+ ions enter the cell, which causes depolarization 4. glutamate neurotransmitters are released

Question 28

What happens in the photoreceptor cell in the light?

Answer 28

1. light strikes cis retinal, which changes it to trans retinal 2. trans retinal dissociates from opsin 3. opsin activates the G-protein transducin, which activates the effector phosphodiesterase 4. the effector breaks down cGMP back to GMP 5. lower cGMP concentration closes Na+ channels 6. cell hyperpolarizes due to Na+ no longer entering the cell 7. glutamate neurotransmitter release is inhibited

Question 29

In what orde are cells involved in visual processing?

Answer 29

1. cones/rods 2. bipolar cells 3. ganglion cells

Question 30

In the light: Cones/rods are ____, which ____ glutamate release onto the bipolar cell. Bipolar cells are then ____, which ____ glutamate onto ganglion cells. Ganglion cells are then ____, which allows it to ____.

Answer 30

hyperpolarized; decreases depolarized; increases depolarized; send signal to the brain

Question 31

In the dark: Cones/rods are ____, which ____ glutamate release onto the bipolar cell. Bipolar cells are then ____, which ____ glutamate onto ganglion cells. Ganglion cells are then ____, which ____.

Answer 31

depolarized; increases hyperpolarized; reduces hyperpolarized; prevents signal to the brain

Question 32

You turn on a light so you can get a glass of water. At the moment the light turns ON, the relative amound of G⍺-GDP of trimeric G proteins ____.

Answer 32

decreases | when G⍺ is activated, GDP --> GTP

Question 33

If the stereocilia of one hair cell becomes permanently bent away from the kinocilium, what would happen?

Answer 33

a single pitch will no longer be perceivable depending on the hair cell's location